EEG Biofeedback Device

Ashley Anderson, Michelle Lorenz, Shikha, Ryan Thome, Chris Wegener

Client: Dr. Daniel Muller Advisor: John Webster

University of Wisconsin - Madison Biomedical Engineering Design Courses

INTELLECTUAL PROPERTY STATEMENT

All information provided by individuals or Design Project Groups during this or subsequent presentations is the property of the University and of the researchers presenting this information. In addition, any information provided herein may include results sponsored by and provided to a member company of the Biomedical Engineering Student Design Consortium (SDC). The above information may include intellectual property rights belonging to the University to which the SDC may have license rights. Anyone to whom this information is disclosed: 1) Agrees to use this information solely for purposes related

to this review; 2) Agrees not to use this information for any other purpose

unless given written approval in advance by the Project Group, the Client / SDC, and the Advisor.

3) Agrees to keep this information in confidence until the

University and the relevant parties listed in Part (2) above have evaluated and secured any applicable intellectual property rights in this information.

4) Continued attendance at this presentation constitutes

compliance with this agreement.

Problem Statement

Design and build an inexpensive, portable electroencephalogram (EEG) that teaches meditation

practitioners to achieve optimal meditation by the presence of EEG alpha and theta waves.

Meditation

Proven form of alternative medicine Epilepsy Addiction AD/HD Mood Disorders

Learned ability Allows self-

detachment and relaxation

Electroencephalograph

Measure surface voltage on the scalp

Brain activity type inferred by frequency

Target frequencies: Alpha (Relaxed) 8-15Hz Theta (Meditative) 4-7Hz

Design Constrains

Handheld/Portable Inexpensive (<$100) Easy to use Must provide interpretable

feedback Unintrusive Comfortable

Coaxial cable headband designoverview + components

Advantages:

- Utilizes economical and user friendly materials (no lengthy preparation necessary)

- Electrode arrangement desirable (frontal placement successful in previous groups)

parts list• headband

• elastic

• shielded audio cable

• male plastic coax plug

http://openeeg.sourceforge.net/buildeeg/images

Disadvantages:

- Setup is rather bulky

- Electrolyte solution is salt water, leaving evaporation as a major issue

• sponge ear plugs

• heat shrink tubing

• 5 pin DIN plug + socket

• table salt (electrolytic solution)

Total cost ≈ 50 dollars

Coaxial cable headband designadditions/improvements

- Wedges as a component of the headband (either included in the band or added by us) to part the hair for better scalp contact

or

manufacture of individual electrodes utilizing concept of asimple hair clip/comb to move hair away from scalp

- Electrolyte medium: current proposed mixture is messy, goal is a non-irritating solution or gel that reduces oil on scalp and maximizes conductivity

Pin Electrodes

An array of metal conducting pins are fixed to an electrode base board.

Between 16 and 32 holes are drilled in the base board and the pins are soldered in place from the back.

Two separate electrodes are attached to a headband and held firmly against the scalp.

http://uazu.net/eeg/ae.html

Pin Electrodes

Advantages Does not require

abrasive skin cleaning or messy conducting gels

Pins are able to burrow through the hair and make direct contact with the scalp

Electrodes are reusable

Disadvantages Lack of conducting gel

may result in poor signal quality

Lack of adhesive leaves the electrode prone to sliding along the scalp, causing signal interference.

Continued

Plate/Disc ElectrodesFeatures:

Most commonly used electrode today in EEG biofeedback devices.

The disc electrodes consists of a flat disc generally of diameter 6mm – 10mm.

EEG disc electrodes feature a hole in the top for electrolyte injection.

Attached to color-coded shielded lead wires.

Cost: $85-90 (for Set of 6)References:Text: http://openeeg.sourceforge.net/doc/hw/electrodes/ http://www.grass-telefactor.com/products/electrodes/electprecintro.htmlFigure 1: http://www.nihonkohden.com/products/supplies/eeg-electrodes.htmlFigure 2 and 3: http://www.electrodestore.com/EEG/EEG.lasso?ran=355D2CB5&S=10&T=37

Figure 1

Figure 2

Figure 3

Plate/Disc Electrodes

ADVANTAGES: Easy to make (just buy them!) Passive Electrodes Pleasing Aesthetics

DISADVANTAGES: Bad conductivity and signal Difficult to use/meditate Dependence on gel Expensive: Extra cost of gel Difficult to clean

Figure 1

Figure 2Reference: Figure 1: http://www.adinstruments.com/products/product.php?id=MLAWBT9Figure 2: http://openeeg.sourceforge.net/doc/hw/electrodes/

Continued

Amplifier Constraints

• Low cost• Clear, accurate

signal• Portable

• Battery powered• Minimal size and

weight• Safe to use

Amplifier Design

• High input impedance• Common Instrumentation Amplifier Design• High CMRR, amplify 50μV P-P• 4 – 15Hz Frequency Bandwidth

Ease of Ease of manufacturemanufacture ComfortComfort

PreparatioPreparation n

simplicitysimplicityCostCost AestheticsAesthetics

Durability Durability (reusability(reusability

))Overall

Coaxial cable

headband8 6 8 9 7 8 7.6

Pin electrodes 2 4 10 4 7 10 6.2

Plate electrodes 10 4 2 1 3 6 4.3

Comparison of electrode designs

Coaxial cable and pin electrodes both reasonably match our project design goals, but further differentiation will depend upon signal strength and quality which we hope to learn from future experiments.

Scale from 1 (lowest) to 10 (highest)

Future Work

• Decide on digital or analog signal processing

• Choose feedback mechanism• Test electrode signal quality• Build amplifier prototype

Questions?